On Tue, 25 Apr 2023, David P. Reed via Starlink wrote:
Ideally, the initial acceleration of a rocket would be better imparted by an external
launcher (at least on the Earth - not initially on Mars). For example, an electromagnetic
linear accelerator that contains the rocket while it accelerates. (We're not talking a
sub-launched missile or a carrier-launched airplane here, and even on carriers,
electromagnetic catapults have been developed that work better than steam ones - despite
Trump's Musk-like idiotic statement that "steam is the best way" for carriers).
The reusability of an electromagnetic launcher is clearly far better than for the
"reusable" launch stage that holds the equivalent energy in fuel form. (snark: and Musk
is a genius who "invented" a whole system for using tubes and magnets called Hyperloop).
It doesn't need to be a tube, it could be a "rail" (railguns work, and are cool
in SF, too).
Powering it just needs a way to store and release electrical energy fast - a
battery, basically, which can be wired up as a collection of storage cells in
parallel.
And this wouldn't pollute the atmosphere anywhere near as much, I'd guess.
also not a rocket engineer, but I've been paying attention for a while
are you aware of spinlaunch? they are trying to get their initial velocity with
electricity, via spinning the rocket at the end of an arm rather than a linear
accelerator.
re: linear accelerator
1. you want to gain alititude quickly to get out of the thickest air, that takes
a launch up the side of a mountain, not something horizontal.
2. having your velocity really high as you leave the launch facility (as opposed
to as you gain speed at higher altitudes) will significantly increase your
aerodynamic forces
3. good mountains don't tend to have ocean to the east for problems to fall
into, even on islands you tend to have population pretty close
4. this is a LOT of mass to move, yes, the more you can power with the linear
accelerator, the less you need in the rocket, but you still need to move a LOT
of mass.
5. rockets aren't stressed to be on their side (at least not when fully
assembled and fueled), adding structure to support this will reduce your gains
6. you will need to mount the rocket to a sled, there's not a lot of ferris
metal in a rocket for magnets to grab
7. there are a lot of delicate electronics on a rocket, how will they handle the
very strong magnetic fields (even if you have them focused on a sled, they will
need to be strong enough that they could be a risk even further away
all these things said, I would love to see someone try it. I think that an
accelerator up the side of a mountain could do wonders for unmanned cargo.
Possibly not electronics, but a lot of structure, and more importantly fuel,
could be launched this way.
But until we have a much more substantial presense in space, I don't see it
worth anyone investing the money to make it work. The F9 reusability was
criticised as being unneded, the Starship is being criticised as being unneeded.
(both with the argument that there wasn't enough demand to need them). I expect
demand to grow with capacity, and as the cost comes down, outstripping the
capacity, but we have a ways to go.
David Lang
_______________________________________________
Starlink mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/starlink
_______________________________________________
Starlink mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/starlink
